Method for RF card detection in a contactless system

a contactless system and card detection technology, applied in the field of detecting cards, can solve the problems of not being able to detect the presence of multiple cards, and occasionally occur collisions

Active Publication Date: 2006-08-10
ATMEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When a reader communicates with the transponders or cards within its fields, collisions occasionally occur if more than one transponder or card tries to reply to the reader at the same time.
However, using this approach, the presence of multiple cards may not be detected until the responding card is removed from the field or the state where it can respond to requests from the reader.

Method used

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  • Method for RF card detection in a contactless system
  • Method for RF card detection in a contactless system
  • Method for RF card detection in a contactless system

Examples

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Embodiment Construction

[0012] The commands used in the embodiments described below are commands for Type B signaling described in the ISO / IEC 14443 standard. However, commands from other standards and / or other signaling schemes may be employed in other embodiments. The relevant commands are: Request B (“REQB”); Wake-Up B (“WUPB”); Slot Marker (“MARKER”); Proximity Card Selection Command (“ATTRIB”); and Halt B (“HLTB”).

[0013] REQB sends a polling request out to all Anticollision state proximity cards (“PICCs” or “cards”). When this command is sent, the number of timeslots, “N,” is assigned to the PICCs, which then choose a random value from 1 to “N” as their timeslot assignment. PICCs choosing the timeslot value “1” will respond with an Answer to Request of Type B (“ATQB”) immediately. The value for “N” is reassigned and new random timeslots are chosen with every REQB and WUPB (discussed below) command.

[0014] WUPB is similar to REQB with one difference. When the WUPB command is sent, cards in the Halted ...

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Abstract

A method and processor-readable storage medium for performing the method of identifying RF cards in a card reader's field. Polling requests are sent to cards in a card reader's field. Where a clear response from the sent command is received from a responding card, the response is saved, the responding card moved to an Active state, and the timeslot number incremented if possible and the above steps repeated until no clear response is received. Where no clear response is received, a determination of whether a collision has occurred is made. If no collision occurred, the timeslot number is incremented; if a collision did occur, another polling request is sent. Discovered cards are returned when no cards or collisions are detected after every timeslot is polled.

Description

FIELD OF THE INVENTION [0001] This invention relates to detecting RF cards within an RF card reader's field. BACKGROUND ART [0002] Radio frequency identification (“RFID”) is becoming increasingly common. RFID uses wireless radio communications to identify and collect information about objects. Information about an object may be created or updated “on the fly” after the object is identified. RFID may be used in a wide range of applications including identity cards. [0003] RFID systems consist of one or more readers and transponders, contactless memory tags that communicate with the reader. Transponders may be carried on identity cards. The transponders contain data allowing the card to be identified and are made of a memory associated with a radio frequency communication block. The reader is connected to an antenna which transmits and receives the radio frequency signal to and from the transponders. In FIG. 1, a reader 68 of the prior art may communicate with all the cards 70, 72, 74...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G06K7/08
CPCG06K7/0008G06K7/10039
Inventor DRESSEN, PHILLIP D.
Owner ATMEL CORP
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